Fasten the retention system (chin strap) as tight as possible under your jaw without causing pain. There must be no slack in the strap, and the strap must be snug up against your jaw. If the retention system is not tight, your helmet may become dislodged or knocked off in an accident.
Do not rely on the snap to secure the helmet. The snap is provided only to prevent the strap from flapping in the air. Fasten the retention system only in the following manner: